1. Field of the Invention
The present invention generally relates to techniques for controlling emissions from dual seals of a variety of types of equipment, such as pumps, valves, compressors, turbines, agitators, centrifuges, mixers and generators, and, more particularly, is concerned with a method for controlling barrier fluid (liquid or gas) leakage from a dual seal so as to maintain a proper level of barrier fluid pressure in the dual seal.
2. Description of the Prior Art
In the past few years the Environmental Protection Agency (EPA) of the U.S. Government has developed new regulations pertaining to emissions of volatile organic compounds (VOCs). The focus of these new regulations is the atmospheric emission of VOCs from chemical and petroleum processing equipment. Many VOCs change phase from a liquid to a gas and become airborne pollutants when leaked from processing equipment. Leakage of VOCs from valves, fittings and mechanical pump seals (the three primary sources of VOC emissions) is referred to as "fugitive" emissions.
Engineers from the chemical and petroleum process industry, along with representatives from the EPA, have worked jointly to develop design guidelines for mechanical seals to control fugitive emissions. One such guideline requires the use of dual mechanical seals with a pressurized non-volatile benign barrier fluid between the seals. Pressurization of the barrier fluid is regulated to ensure a correct pressure range relative to the pumpage fluid pressure, and the system is monitored to detect leakage from the seals.
Current pressurized barrier seal designs, although effective, require support equipment that must be adjusted, carefully monitored and maintained. In addition, there is not a system available which quantitatively measures the leakage of pumpage or barrier fluid.
Consequently, a need exists for an effective fugitive emissions sealing system in which barrier fluid leakage is measured and compensated so that its proper pressurization is maintained.